This invention relates to the manufacture of heat insulated glass or crystal articles, and more particularly to the manufacture of drinking glasses, decanters, vessels, etc., provided with a lining made of a heat insulating material, which lining is permanently fastened to the bottom and side walls of the glass article for the purpose of conserving the temperature of its contents for a relatively long period of time.
As is known, a liquid contained in a drinking glass at a temperature different from atmospheric temperature undergoes a rapid temperature change due to thermal conductivity through the walls of the glass. This temperature change takes place at a slow and decreasing rate until equilibrium between the liquid temperature and the surrounding medium temperature is reached. This thermal conductivity of glass or crystal is inconvenient when it is desired to conserve the liquid at a temperature substantially different from ambient temperature. Also, the heat developed by the hand of the user while holding the drinking glass or vessel is transmitted through the wall of the vessel, thus increasing the temperature of the contents to a level higher than ambient temperature. Moreover, when the contents of the drinking glass or vessel is at a very low temperature with regard to the temperature of the user's hand, the glass rapidly takes such inner lower temperature, thus causing an unpleasant sensation to the user holding the glass during a long period of time, while the heat exchange is taking place.
Further, when a glass is used to contain cold drinks of any type, the external wall of the glass cools down rapidly, thus causing condensation of atmospheric water vapor, and water droplets deposit on such external surface. The water droplets progressively increase in size, join together and slide down the walls to the base of the glass, and then deposit on the surface of the piece of furniture that supports the glass, thus leaving portions of water on the piece of furniture. This of course damages the furniture when it is made of a material sensitive to water. This condensation of moisture on the external wall of the glass is also an inconvenience to the user, since his hands become wet when holding the glass to drink its contents.
With the purpose of avoiding these inconveniences, and particularly when the glass is used for cold liquids, or when it contains pieces of ice, it is customary to use glasses with thick bottoms and walls, such as those used for whiskey, with the purpose of offering resistance to the flow of heat. However, heat transfer is not prevented, but merely takes place at a slower rate, and after a time the same unpleasant effects takes place. Sometimes, to avoid the formation of water on furniture, it is customary to put the glass on special seats, or to insert the glass into hollow cylindrical bases which are made of different types of materials and which receive the water condensed on the outside of the glass, thus preventing the water from spreading onto the piece of furniture.